1. Field of the Invention
The invention relates to molded castings from mineral wool, obtained notably through a process of vacuum casting, displaying specific properties resulting from the addition of solid particles and in which the mineral fibers are stabilized by a bond. The invention also relates to processes for the manufacture of such a molded casting.
2. Discussion of the Background
Molded castings from mineral wool, used in particular as setting plates or as bushings for encasing pipes, generally are manufactured by dispersing mineral wool in a bond suspension, then draining and drying the mineral wool thus prepared on a draining mat or in a mold by vacuum suction. Silica sol and starch are known to be used as bond. The mineral wool is, for example, rock wool, glass wool, aluminosilicate wool, or a combination of these products.
This process also makes it possible to color the mineral wool completely, by adding a colorant to the bond suspension. For a black coloration of the molded casting, an appropriate blackening agent thus is added, for example activated carbon, carbon black or printer's black.
To obtain an adequate incrustation of the solid particles on the fibers and achieve therein a uniform bonding with the aid of the bond and/or assure a uniform coloring of the final product, the silica sol, starch, color pigment must be added to the water in sufficient quantity. In practice, one always works with an excess of bond, a not-insignificant quantity of which turns up in the suctioned water.
This excess of bond in the suspension induces the formation of colloids and thus a thickening of the dispersion, which is not favorable to a good incrustation and a uniform distribution in the wool. Apart from this initial problem, this residual bond content involves contamination of the suspension by micro-organisms on the occasion of each prolonged interruption, for example during the weekend, so that the suspension must be renewed each time.
If colorants also are used, the waste water must be filtered of all its colorant particles before being discarded into the sewer. This excess of bonds and pigments thus involves not only an increase in the cost of the raw material, but also in the cost of formation and of purification of waste waters. Furthermore, it can be noted in the final product, particularly when it is colored in bulk, that the mineral fibers are overladen with solid particles, which in turn involves a degradation of the desired properties.